Envelope for flat cathode tubes with lower sections of front and rear walls similarly displaced



3 l 3 22 a QR 3 9 30 9 55 l March 14, 1967 w. R. AIKEN 3,309,551

, ENVELOPE FOR FLAT CATHODE TUBES WITH LOWER SECTIONS OF FRONT AND REAR WALLS SIMILARLY DISPLACED Filed June 1, 1964 W Cy z 10 J 41 I i2- ,z

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WILLIAM ROSS AIKEN United States Patent ENVELOPE FOR FLAT CATHODE TUBES WITH LOWER SECTIONS OF FRONT AND REAR WALLS SIMILARLY DISPLACED William R. Aiken, 10410 Magdalena Ave., Los Altos Hills, Calif. 94022 Filed June 1, 1964, Ser. No. 371,664 2 Claims. (Cl. 31379) The present invention relates to the envelopes of cathode ray tubes. More particularly, the present invention relates to envelopes to the fiat cathode ray tubes known as the Kaiser-Aiken tubes.

Upon evacuation of such envelopes, the large front and rear walls of the envelopes must withstand substantial atmospheric pressures in a direction perpendicular to their surfaces, and when materials of low tensile strength, such as glass, are used in the construction of the envelopes, it has been necessary to make the walls of such envelopes of substantial thickness so that they may withstand these pressures. This renders the envelopes heavy and increases their cost. The problem of constructing envelopes for fiat cathode ray tubes, that withstand the atmospheric pressures directed against their large side surfaces is complicated by the fact that the flat cathode ray tubes are usually constructed to comprise upper and lower sections which are offset relative to each other in a direction perpendicular to the planes of their front and rear walls. As explained in my US. Patent No. 2,928,014 the lower section is designed to accommodate the elements for deflecting the electron beam in an upward direction into a vertical plane substantially parallel to the rear wall of the tube; and the upper section contains, adjacent to said rear wall, the elements for deflecting the upwardly directed beam toward and into impingement with the phosphor screen which is usually provided upon the inner surface of the front wall of the tube envelope. To provide sufficient space for the upwardly directed electron beam to be bent effectively into impingement with the phosphor screen on the front wall of the tube, it is desirable that the vertical plane into which the electron beam is bent by the deflection elements in the lower section of the envelope extend close to the vertically superimposed deflection elements along the rear wall of the envelope. This makes it advantageous to displace the lower section of the tube envelope to a limited degree in a direction perpendicular to, and rearwardly away, from the target area of the upper section. When the upper and lower sections of a flat envelope are offset in the described manner, the bent transition areas between the upper and lower sections of the front and rear walls of the envelope are stress areas that are particularly vulnerable and which break frequently during the evacuation process of the envelope or later when the tube is uncautiously handled during use.

It is an object of my invention to provide a pressure resistant off-set tube envelope of the type referred to.

Another object of the invention is to provide an envelope construction for cathode ray tubes of the type referred to, whose front and rear walls are capable of withstanding substantial pressures without need to resort to increased wall thickness or special reinforcing structures.

In the accompanying drawing:

FIGURE 1 is a perspective of a fiat envelope, for cathode ray tubes, that is constructed in accordance with my invention;

FIGURE 2 is a cross-section through the envelope taken along line 22 of FIGURE 1, with various components of the assembled cathode ray tube indicated schematically in their proper location; and

FIGURE 3 is a fragmentary cross section, similar to 3,309,551 Patented Mar. 14, 1967 ICC FIGURE 2, through a modified embodiment of the invention.

The tube envelope constructed in accordance with the invention has a larger upper section 10 whose front wall 12 constitutes the picture area of the tube, and a smaller lower section 14 which is rearwardly displaced relative to the upper section. In accordance with the invention the connecting wall portions 16 and 18 between the front wall sections 12 and 20 and the rear wall sections 22 and 24, respectively, extend in planes substantially perpendicular to the plane of the surfaces of said sections.

By providing an abrupt offset between the upper and lower sections of the tube envelope, instead of a gradual transition such as is conventional practice, the connecting wall portions 16 and 18 between the front wall sections and the rear wall sections of the envelope, which were formerly the most vulnerable areas of the envelope, are effectively converted into strengthening ribs whose edges face the direction in which the atmospheric pressure is potentially most dangerous to the evacuated envelope, i.e., the direction perpendicular to the planes defined by the large front and rear Wall areas of the tube. In an edgewise direction even a relatively thin sheet of glass can Withstand very high pressures without breaking. In addition, the defined disposition of the connecting portions 16 and 18 of the front and rear wall sections of the envelope is effective to divide the unsupported spans constituted by the front and rear walls of conventionally constructed flat tube envelopes, into two tandem-p0sitioned spans of substantially shorter length and exposes each of said shorter spans to substantially lesser loads of atmospheric pressure than the total pressure exerted by the atmosphere upon the front and rear Wall of conventionally constructed flat tube envelopes of comparable size. As a result thereof, the total envelope may now be made from plate glass of significantly smaller wall thickness than formerly necessary. This reduces the cost of the tube, and yet the resultant structure is more pressureresistant than the heavier and more costly envelopes of conventional design.

The described cross-sectional conformation of the tube envelope is of particular advantage for tubes that are partially made from material other than glass, such as ceramic or cement-like materials. In tubes of this type, all of the lower section 14 of the envelope and both the connecting ribs 16 and 18 are made from ceramic or cement-like materials, and the upper rear wall section 22, the end walls 30 and the top wall 32 of the upper section 10 are likewise made from ceramic or cement-like materials (Figure 2). The upper front wall section 12, however, which constitutes the picture area of the tube, is made from a sheet of transparent glass that is secured to the edges of the top wall and of the side walls of the upper section 10 and the front edge of the connecting rib 16 in a gas tight manner, such as by fusing the peripheral area of the sheet of glass through copper strips to the edges of the named components of the tube envelope. The existence of the connecting rib 16 which extends in a plane parallel to the potentially most harmful direction in which pressure is exerted by the atmosphere upon the tube envelope, makes it possible to establish between the lower section 14 of the envelope and the glass plate 12 a seal which is strengthened rather than strained by the pressure of the atmosphere in a direction perpendicular to the planes of the front wall sections of the envelope; and by raising the front wall 20 of the lower section 14 of the tube envelope above the level of the connecting rib 18 between the sections of the rear wall as best shown in FIGURE 2, it is possible to confine the size of the glass plate 12 to precisely the area that can be reached by the twice-deflected electron beam 32. The lower boundary of said area is primarily determined by the beam bending effect of the lowest of the vertical deflection elements 36 in the upper section 10 of the tube. This again makes it possible to employ a glass sheet of lesser thickness for the picture area, with resultant reduction in the weight of the tube and concomitant saving in cost.

Furthermore, the shoulder formed by the connecting rib 16 provides a suitable support for one or several stripshaped electrodes such as indicated at 38. Suitable potentials may be applied to these electrodes during performance of the tube through leads 4a to eliminate undesirable electrostatic effects of the rib 16 upon the deflected electron beam and to predetermine precisely the points of impingement of the electron beam in the lower region of the phosphor screen 41.

The described and illustrated cross-sectional confor mation of the tube envelope has the added advantage of permitting proper disposition of magnetic bars 420 and 4211 at either side of the vertical plane into which the electron beam is initially deflected (FIGURE 2). Such bars are employed to establish a magnetic field through which the electron beam passes and which accentuates the bending etlect imparted to the beam by the horizontal row of juxtaposed primary deflection elements 44 in the lower section 14 of the tube envelope, in order that said beam may bend upwardly by a full 90 and may produce a straight raster upon the phosphor screen 41 of the tube upon its secondary deflection by operation of the vertically superposed secondary deflection elements 36 along the rear wall of the envelope. The purpose and operation of magnetic members of the type illustrated at 42:! and 42b in FIGURE 2, is fully explained in my US. Patent No. 2,937,315 for an Electronic Device issued on May 17, 1960, to which reference is made for details. Owing to the configuration of the tube envelope as illustrated in the accompanying drawing and as described hereinbefore, it now is readily possible to locate the magnetic bars 42a and 42b symmetrically at either side of the vertical plane into which the electron beam is deflected by the primary deflection elements 44. Hence, the electron beam passes through uniform regions of the magnetic field established between the magnetic bars 421: and 42b, i.e., regions in which the force lines of the magnetic field are substantially parallel and the deflecting effect of the magnetic field upon the electron beam is therefore uniform at all levels of its primary deflection path.

In the embodiment of the invention illustrated in FIGURE 3, the connecting wall portions 44 and 46 between the front wall portions 48 and 50 and the rear wall portions 52 and 54, respectively, of a tube envelope of the same cross-sectional contour as the embodiment of the invention illustrated in FIGURES l and 2, are made from a substance other than glass, ceramic or concretelike materials, namely, strips of preferably non-magnetic metals which are fused or cemented to the edges of the wall portions 48, 50 and 52, 54.

While I have described my invention with the aid of preferred embodiments thereof, it will be understood that the invention is not limited to the specific constructional details shown and described by way of example which may be departed from without departing from the spirit and scope of the invention.

I claim:

1. An envelope for flat cathode ray tubes comprising relatively spaced front and rear walls, each having an upper and a lower section displaced from each other in the same direction, a first connecting wall portion extending between the upper and lower sections of said front wall in a plane substantially perpendicular to the planes defined by said wall sections and a second connecting wall portion extending between the upper and lower sections of said rear wall in a plane substantially perpendicular to the planes defined by said wall sections and located at a lower level than said first connecting wall portion, said upper front wall section having a phosphor layer upon its inner surface, electrode means in the space between said lower wall sections for deflecting an electron beam upwardly into a vertical plane adjacent the inner surface of said upper rear wall section, and magnetic means at either side of said plane of deflection below said first connecting wall portion and above said second connecting wall portions respectively, for accentuating the upward deflection of the electron beam by said electrode means.

2. An envelope for fiat cathode ray tubes comprising relatively spaced front and rear walls, each having an upper and a lower section displaced from each other in the same direction, a first connecting wall portion extending between the upper and lower sections of said front wall in a plane substantially perpendicular to the planes defined by said wall sections and a second connecting wall portion extending between the upper and lower sections of said rear wall in a plane substantially perpendicular to the planes defined by said wall sections and located at a lower level than said first connecting wall portion, said upper front wall section being transparent and of a material different from the remaining wall portions of said envelope and having a phosphor layer upon its inner surface, first electrode means in the space between said lower wall sections for deflecting an electron beam upwardly into a vertical plane adjacent the inner surface of said upper rear wall section, magnetic means at either side of said plane of deflection below said first connecting wall portion and above said second connecting wall portion, respectively, for accentuating the upward deflection of the electron beam by said first electrode means; second electrode means adjacent the inner surface of said upper rear wall section for deflecting the upwardly deflected electron beam into impingement with said phosphor layer, and third electrode means upon said inner surface of said first connecting wall portion for controlling the level of impingement of the electron beam upon said phosphor layer.

References Cited by the Examiner UNITED STATES PATENTS 2,449,558 9/1948 Lanier et al. 3l3-78 X 2,928,014 3/l960 Aiken et al 3l3-80 X 2,945,974 7/1960 Aiken et al. 3l3-78 X 2,997,621 8/1961 Schlesinger 3l379 X 3,118,084 1/1964 Havn et al. 31378 X 3,l7l,056 2/1965 Gabor 3l380 X 3,207,936 9/1965 Wilbanlzs et al 313-75 JAMES W. LAW RENCE, Primary Examiner.

R. SEGAL, Assistant Examiner. 

1. AN ENVELOPE FOR FLAT CATHODE RAY TUBES COMPRISING RELATIVELY SPACED FRONT AND REAR WALLS, EACH HAVING AN UPPER AND A LOWER SECTION DISPLACED FROM EACH OTHER IN THE SAME DIRECTION, A FIRST CONNECTING WALL PORTION EXTENDING BETWEEN THE UPPER AND LOWER SECTIONS OF SAID FRONT WALL IN A PLANE SUBSTANTIALLY PERPENDICULAR TO THE PLANES DEFINED BY SAID WALL SECTIONS AND A SECOND CONNECTING WALL PORTION EXTENDING BETWEEN THE UPPER AND LOWER SECTIONS OF SAID REAR WALL IN A PLANE SUBSTANTIALLY PERPENDICULAR TO THE PLANES DEFINED BY SAID WALL SECTIONS AND LOCATED AT A LOWER LEVEL THAN SAID FIRST CONNECTING WALL PORTION, SAID UPPER FRONT WALL SECTION HAVING A PHOSPHOR LAYER UPON ITS INNER SURFACE, ELECTRODE MEANS IN THE SPACE BETWEEN SAID LOWER WALL SECTIONS FOR DEFLECTING AN ELECTRON BEAM UPWARDLY INTO A VERTICAL PLAN ADJACENT THE INNER SURFACE OF SAID UPPER REAR WALL SECTION, AND MAGNETIC MEANS AT EITHER SIDE OF SAID PLANE OF DEFLECTION BELOW SAID FIRST CONNECTING WALL PORTION AND ABOVE SAID SECOND CONNECTING WALL PORTIONS RESPECTIVELY, FOR ACCENTUATING THE UPWARD DEFLECTION OF THE ELECTRON BEAM BY SAID ELECTRODE MEANS. 